A gasifier generally includes a primary combustion chamber into which solid fuel is loaded on to a grate structure on which it is first dried and gasified via controlled primary combustion. The resultant gas is then transferred into a secondary combustion chamber, which may conveniently be a cycloburner, for secondary combustion to produce a high temperature relatively clean flue gas able to be used for a variety of purposes, eg. power generation or heating. There is a small residue of inorganic matter.
A gasifier of the general type to which the present invention relates is disclosed, for example in U.S. Pat. No. 4,716,842, and the technology generally is of particular interest in waste recycling, especially with an emphasis on so called “green power” generation. Specific solid fuels which may conveniently be gasified in this way include biological waste, agricultural byproducts, wood waste and biomass.
Problems experienced with gasifiers, as with many other high temperature furnace processes, include sintering or aggregation of solid fines, and the difficulty of achieving thorough mixing of fuel and air/gas streams. It is thought by the inventor that these problems can be minimised over time in the initial gasification process by appropriate design of the grate structure and it is towards this preferred objective that the present invention is especially directed.
U.S. Pat. No. 5,680,824 discloses a grate structure in which moveable hollow grate plates with coolant passages are reciprocable between staitonary grate plates.
The invention seeks to provide an improved grate construction for furnaces generally, but especially for solid fuel gasifiers.